The present invention relates to a ceramic cutting insert for a cutting tool of the type which comprises a tool holder with a seat intended to accept the cutting insert, the shape of which partially corresponds to that of the cutting insert, and a clamp which is connected to the holder via a screw. The object of the clamp is to clamp the cutting insert firmly in the seat, said clamp features a nose provided to grip into one of the two recessed openings on opposite upper and lower sides on the cutting insert so that when the screw is tightened the cutting insert is drawn into the seat so that at least one side surface of the insert is tightly pressed against a corresponding side surface of the seat.
A cutting tool, including a cutting insert and a tool holder in general of the type described above, is earlier known through SE 9401822-3. In this case the recess in the cutting insert has the form of a transverse, cylindrical hole, which like the nose of the clamp is generally cylindrical in shape, although inclined in relationship to the cylindrical hole in the cutting insert. The length of the nose is relatively large, whereby the point of contact between the nose and the cylindrically shaped inner wall of the hole is located relatively far down in the hole. This cutting tool has been found to work largely without problems in practical use.
Another cutting tool is known from EP 0 074 601. In this case the recess in the cutting insert has the shape of an comparatively shallow recess with a basic shape of either a four leaf clover or a figure eight, at the same time the nose of the clamp has a half cylindrical or half barrel like shape, whereby the longitudinal extension of the nose is oriented at right angles to the actual longitudinal extension of the clamp. Through this design a point contact is attained between the nose and the inside surface of the recess. A drawback with this design, however, is that the longitudinal extension of the clamp must always be located in the direction of the bisector between diametrically opposite corpers on a quadrilateral shaped cutting insert, e.g. a square or rhombic shaped insert. For this reason cutting tools of this type are difficult to use in machines where two or more cutting inserts are to be placed near each other.
Irrespective of the type of tool the cutting insert is always a replaceable component with a limited life, whilst the tool holder is of a more long-lived character. In practice the cutting insert can thus have an effective life of some few hours, while the life of the tool holder can extend to months or years. Different types of cutting tools are found on the market. Machine owners must often have different types of tolls to remove different types of inserts. This causes both organizational as well as logistical problems because the different types of cutting inserts and their corresponding clamping tool are often made by different manufacturers.
The aim of the present invention is to solve the above-mentioned problem by creating a new cutting insert for both types of tool. A basic purpose of the present invention is thus to create a ceramic insert which can be used universally for cutting tools according to both SE 9401822-3 and EP 0 074 601 and which furthermore permits the use of variable adjustments of the angular position of the clamp relative to the insert even in those cases when the tool is of the type which is described in EP 0 074 601. An additional purpose is to create a ceramic insert, which lends itself to an easy and economic method of manufacture despite the fact of its ability to fit into both types of tool.
According to one aspect, the present invention provides a ceramic cutting insert for a cutting tool which comprises a holder (1) with an insert seat intended for the acceptance of the cutting insert (3), and a clamp (2) which is connected to the holder to firmly clamp the cutting insert in the seat, said clamp (2) features a nose (4) provided to grip into one of two recesses (5) which have their openings on opposite upper and lower sides (12, 12xe2x80x2) of the cutting insert in order to pull the cutting insert into the insert seat and press tightly at least one side surface in the insert seat wherein the recess (5) has a rotational symmetrical shape an comprises an inner cavity (18) which is delimited by a cylindrical or slightly conical wall surface (19), said cavity extends from the inner cavity and expands outwards by an ever increasing diameter in the direction from the inner cavity to the entrance opening in one of the upper or lower sides (12, 12xe2x80x2), and an external cavity (20) is delimited by at least two ring shaped partial surfaces which extends between the inner cavity (18) and the conical surface (21).